diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/afl-fuzz.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/include/afl-fuzz.h b/include/afl-fuzz.h index c5b01da8..f3a76492 100644 --- a/include/afl-fuzz.h +++ b/include/afl-fuzz.h @@ -1027,11 +1027,17 @@ static inline u32 rand_below(afl_state_t *afl, u32 limit) { } - /* Modulo is biased - we don't want our fuzzing to be biased so let's do it right. */ - u64 unbiased_rnd; + /* Modulo is biased - we don't want our fuzzing to be biased so let's do it + right. See: + https://stackoverflow.com/questions/10984974/why-do-people-say-there-is-modulo-bias-when-using-a-random-number-generator + */ + u64 unbiased_rnd; do { + unbiased_rnd = rand_next(afl); + } while (unlikely(unbiased_rnd >= (UINT64_MAX - (UINT64_MAX % limit)))); + return unbiased_rnd % limit; } |